The Problem of the Sirex 



of an inch thick Is left intact at the end of the 

 vestibule. There Is no other defensive pre- 

 caution; no barricade, no heap of shavings. 

 In order to come out, the Insect has only to 

 pierce an insignificant sheet of wood and then 

 the bark. 



The Nine-spotted Buprestis [Ptosima 

 novemmaculata) behaves in the apricot-tree 

 precisely as the Bronze Buprestis does in the 

 poplar. Its larva bores the inside of the 

 trunk with very low-celllnged galleries, 

 usually parallel with the axis; then, at a dis- 

 tance of an Inch and a quarter or an Inch and 

 a half from the surface. It suddenly makes 

 a sharp turn and proceeds In the direction of 

 the bark. It tunnels straight ahead, taking 

 the shortest road. Instead of advancing by Ir- 

 regular windings as at first. Moreover, a 

 sensitive Intuition of coming events Inspires 

 Its chisel to alter the plan of work. The 

 perfect insect Is a cylinder; the grub, wide In 

 the thorax but slender elsewhere. Is a strap, 

 a ribbon. The first, with Its unyielding 

 cuirass, needs a cylindrical passage; the sec- 

 ond needs a very low tunnel, with a roof that 

 will give a purchase to the ambulatory nip- 

 ples of the back. The larva therefore 

 changes Its manner of boring utterly: yester- 

 day, the gallery, suited to a wandering life 

 213 



